基于强震记录的土层液化识别

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1、重庆大学硕士学位论文II英文摘要ABSRACTLiquefactionisacommonkindofdisastercausedbymajorearthquakes.Specialattentionsshouldbepaidtothisfieldinseismicengineering.Chinaisacountrywithvastterritorywhichiseasilysubjectedtoseriousliquefactiondisaster.Theresearchinsoilliquefactionhasbeenanimportanttopicinseismicengineerin

2、ginChina.Duringearthquakes,itisthemaincontentinreal-timeearthquakedisasterreductiontoquicklyidentifywhetherthesoilliquefactionoccursanditsextentbasedonstrongmotionrecords.Atpresent,therearefivemethodsavailabletoidentifyliquefaction,i.e.,Miyajimamethod,Suzukimethod,KostadinovandYamazakimethod,HHTbas

3、edmethodandthemethodbasedonfrequencydecreaserate.Inthispaper,thesefivemethodsforliquefactiondetectionaresystematicallycomparedfirst.Foreachmethod,parametersintroducedincalculationandtheliquefactioncharacteristicsofgroundmotionsareanalyzed.Then,someimprovementstoexistingliquefactionidentificationmet

4、hodsaresuggestedandtwomethodsforliquefactionidentificationareproposedbasedonsurfacestronggroundmotionsandboreholegroundmotionsrespectively.Incasethatonlysurfacegroundmotionsareavailable,thedecreaserateofinstantaneousfrequencyisusedtoidentifytheliquefactionofsoil.First,theinstantaneousfrequencyofstr

5、onggroundmotioniscalculatedbyusingtime-varyingARMAmodel.Atthesametime,theintensityenvelopeisusedtodescribethenon-stationarycharacteristicsinintensityofgroundmotions.Correspondingtotheriseanddeclineofthestrengthenvelope,themeanvaluesofinstantaneousfrequencyforthesetwosegmentsarecalculatedseparatelyw

6、hicharerespectivelytakenastheinitialvalueandthefinalvalueofinstantaneousfrequency.Thenthetimeduringwhichtheinstantaneousfrequencydecreasefromtheinitialvaluetothefinalvalueandtherelativeproportionoffrequencydecreaseareusedtoidentifywhethersoilliquefactionoccursinthissite.Incasethatboreholerecordsare

7、available,themethodbasedonsystemidentificationisused.Inthismethod,borehole(baserock)recordisusedastheinputandthesurfacegroundmotionrecordisusedastheresponse(output)withthesoilbetweenthesetworecordsasthestru